Try zero cushions and enough to have your head touching the roof and you will see.
Those that have the seat on its upper limit more than likely won't have experenced the parallax in the vertical plane.
Those of us that arn't vertically challanged and arn't eyes level with the altimeter at the top of travel are quite aware of it like the previosu poster has mentioned having to squidge down to a more horizontal view to get rid of it.